Effects and safety of metformin in patients with concurrent diabetes mellitus and chronic obstructive pulmonary disease: a systematic review and meta-analysis

Aim: This study aimed to investigate the effects and safety of metformin in patients with concurrent diabetes mellitus (DM) and chronic obstructive pulmonary disease (COPD). Methods: PubMed, Embase, Web of Science, the China National Knowledge, and Cochrane Database were searched to find studies that examined the effects and safety of metformin in patients with concurrent DM and COPD. We conducted a meta-analysis with a risk ratio (RR) and assessed the quality of included studies and pooled evidence. Results: Eight studies were involved. Metformin was associated with lower risk of COPD-related hospitalizations (RR: 0.72, 95% CI: 0.53-0.98; I-2= 89%) and all-cause mortality (RR: 0.60, 95% CI: 0.36-1.01, I-2= 69%) in patients with concurrent DM and COPD, but did not increase the risk of hyperlactatemia (RR: 1.14, 95% CI: 0.92-1.41, I-2 = 8%). Conclusions: Metformin use is associated with lower risk of COPD-related hospitalizations and risk of all-cause mortality without increasing the risk of hyperlactatemia. Considerations should be given to conduct more high-quality randomized trials involving larger samples.